The gathering in Baden-Baden will be the first occasion for the leaders to discuss global economic challenges since US President Donald Trump took office in January.

The G20 nations have been in agreement that they oppose any forms of protectionism and encourage free trade as a way to foster the world economy.

But the Trump administration is taking a protectionist stance. It calls it part of an effort to save US jobs.

On top of possible hikes in tariffs on imports, Washington has suggested it may ignore any ruling by the World Trade Organization that it sees as an affront to US sovereignty. Analysts are watching what arguments the US will present at the G20 meeting.

Finance Minister Taro Aso and Bank of Japan Governor Haruhiko Kuroda will represent Japan.

Aso is scheduled to hold his first meeting with US Treasury Secretary Steven Mnuchin on the sidelines of the G20 talks. Attention is focused on what they will discuss concerning foreign exchange policies and a new bilateral economic dialogue.

Tokyo and Washington are coordinating meetings between Aso, who doubles as deputy prime minister, and Vice President Mike Pence in mid-April.